The present invention relates to angiogenesis inhibitors containing cysteine derivatives as active ingredients and particularly provides drugs which are useful for treatment of ophthalmopathy such as retinal diseases.
Homeostasis of blood vessels is maintained by various functions of endothelial cells. The vascular endothelial cells have 1) an effect of mediating transportation of necessary components such as nutrition in blood to tissues and preventing unnecessarily much components from passing, 2) an effect of circulating blood smoothly without coagulation, 3) an effect of stopping bleeding when the blood vessels are transected, and 4) a regulatory effect of keeping vasotonia constant.
Angiogenesis occurs stepwise as follows; decomposition of a basement membrane by protease produced in the vascular endothelial cells, migration and proliferation of the vascular endothelial cells, lumen formation of the vascular endothelial cells, formation of the basement membrane and encirclement of peripheral cells. The angiogenesis is closely related to various diseases, particularly retinal diseases such as diabetic retinopathy, macular degeneration, retinal vein occlusion and retinal artery occlusion, neovascular glaucoma or tumors such as hemangioma.
On one hand, WO 91/08199 discloses that cysteine derivatives (general formula [I]), which are active ingredients of the present invention, are useful compounds as therapeutic agents for immunodeficiency, autoimmune diseases and the like. However, there have been no report relating to their effects of inhibiting the angiogenesis or their effects of treating retinopathy.
It is a very interesting subject to find further new pharmacological effects of these cycteine derivatives, which have been useful drugs.
The present inventors studied effects of cysteine derivatives on angiogenesis in order to find new pharmacological effects thereof. As a result, it was found that the cysteine derivatives had inhibitory effects on angiogenesis and were useful as therapeutic agents for diseases in which the angiogenesis participates, particularly retinal diseases such as diabetic retinopathy, macular degeneration, retinal vein occlusion and retinal artery occlusion, neovascular glaucoma and tumors such as hemangioma.
The present invention provides angiogenesis inhibitors and therapeutic agents for retinal diseases containing compounds represented by the following general formula [I] or salts thereof (hereinafter referred to as xe2x80x9cthe present compoundxe2x80x9d) as active ingredients. 
[wherein R1 and R2, being the same or different, are hydrogen, lower alkyl, lower alkanoyl, phenylcarbonyl, phenyl-lower alkyl or phenyl-lower alkoxycarbonyl.
R3 and R4, being the same or different, are hydroxy, lower alkoxy, amino or lower alkylamino.
A1, A2 and A3, being the same or different, are straight-chain or branched lower alkylene.
xe2x80x9cmxe2x80x9d is 0 or 1.]
The groups defined above are described in more detail. The lower alkyl is straight-chain or branched alkyl having one to six carbon atoms such as methyl, ethyl, propyl, hexyl, isopropyl or t-butyl. The lower alkanoyl is straight-chain or branched alkanoyl having two to six carbon atoms such as acetyl, propionyl, hexanoyl, isopropionyl or t-butanoyl. The lower alkoxy is straight-chain or branched alkoxy having one to six carbon atoms such as methoxy, ethoxy, propoxy, hexyloxy, isopropoxy or t-butoxy. Examples of particularly preferred compounds are N1-(6-aminohexyl)-N2-(2, 2-dimethyl-3-mercaptopropionyl)-L-cysteinamide represented by the following formula [II] or salts thereof. 
The above-mentioned salts can be pharmaceutically acceptable salts with organic or inorganic acids or bases, and examples of such salts are hydrochlorides, hydrobromides, sulfates, phosphates, lactates, maleates, fumarates, oxalates, methanesulfonates, p-toluenesulfonates, sodium salts, potassium salts, calcium salts, magnesium salts, zinc salts, ammonium salts, triethanolamine salts, dicyclohexylamine salts and the like.
There are optical isomers and diastereomers in the present compound, and drugs containing these isomers or diastereomers as active ingredients are also included in the present invention. The present compound can take the form of a solvate such as a hydrate.
In order to study utility of the cysteine derivatives represented by the general formula [I], the inhibitory effect of the present compound on angiogenesis was examined. Details will be described in the part of the pharmacological test later. It was found that the present compound had an excellent inhibitory effect on angiogenesis of a chick chorioallantonic membrane, which is an in vivo angiogenesis evaluation model. From this result, the present compound is expected to be useful as the therapeutic agents for the diseases in which the angiogenesis participates, particularly the retinal diseases such as diabetic retinopathy, macular degeneration, retinal vein occlusion and retinal artery occlusion, neovascular glaucoma and the tumors such as hemangioma.
The present compound can be administered orally or parenterally. Examples of dosage form are tablets, capsules, powders, granules, percutaneous absorbents, injections, eyedrops, eye ointments and the like. The present compound can be formulated into preparations with a pharmacutical carrier using conventional techniques. For example, oral preparations such as tablets, capsules, granules and powders can be produced by adding optionally diluents such as lactose, crystalline cellulose, starch and vegetable oil; lubricants such as magnesium stearate and talc; binders such as hydroxypropylcellulose and polyvinyl pyrrolidone; disintegrator such as calcium carboxymethylcellulose or low-substituted hydroxypropylmethylcellulose; coating agent such as hydroxypropylmethylcellulose, macrogol or silicone resin; or film forming agent such as gelatin film. Eyedrops can be produced by adding isotonic agents such as sodium chloride and concentrated glycerine; buffers such as sodium phosphate and sodium acetate; surfactants such as polyoxyethylenesorbitan monooleate, polyoxyl 40 stearate and polyoxyethylene hydrogenated castor oil; stabilizers such as sodium citrate and disodium edetate; preservatives such as benzalkonium chloride and paraben; and the like. pH can be in a range acceptable for ophthalmic preparations, and it is more preferably in a range of 4 to 8.
The dosage of the present compound can be selected suitably according to the symptoms and age of the patient (e.g. human) and dosage form and the like. In case of the oral preparation, the present compound can be administered once to several times per day with a daily dose of 0.1 to 5000 mg, preferably 1 to 1000 mg.
Results of the pharmacological test are shown below, and they are intended for better understanding the present invention but are not to limit the scope of the present invention.